I guess for me it is about image. As with most things, my style is an ongoing thing. I'm slowly learning what works for me and what doesn't. I try to dress in a way that is the most flattering to my body. I also try to dress in a way that says something about who I am and what I like. I like trying to pick the right thing to wear for a given occasion whether it be going to class, going out drinking, dancing, to a show, a movie, etc.
I feel the same way about my hairstyle. I'm trying to find a haircut that suits my style and flatters my head shape the best. I have a fairly large head so I now have a hairstyle that covers my forhead. I've had a lot people tell me my hair looks far better now then when it was shorter.
I guess my reasons are pretty vain but perception has always interested me. I like to look at someone, how they are dressed, how they speak, their hairstyle, the way they carry themselves, who they are friends with etc and see what conclusions I can draw about them before I even speak to them. I'm still surprised the odd time when I meet someone who is completely different than I expected. Most of the time, I can accurately tell a lot about someone just by observing them for a while.
I guess I use what I have learned by watching other people and try to make an image for myself that projects exactaly what I want it to say about myself.